The contents and disclosure of U.S. patent application Ser. No. 11/596,839, filed Nov. 17, 2006, as well as PCT Patent Application Serial No. PCT/05/22233, filed Jun. 22, 2005, and U.S. Provisional Patent Application Ser. No. 60/582,036, filed Jun. 22, 2004 are hereby incorporated by reference herein in their entirety.
The main problem in the honing process is related to the position feedback and therefore the derivatives of it (velocity, acceleration and jerk). This problem is presently being solved mostly by using dedicated mechanical systems; where the control is done by setting hard limits locking of any adjusting response or simply offering a faulting output as safety response. This is representative of four bar linkage systems. The fast reciprocating motion makes a close loop control historically difficult and expensive.
The present method and system concept is related to the feedback information offered by the servo system and the optimization process related to system dynamic output (position, velocity and acceleration) and tool performance. The stroking process in a honing machine is the relative motion between the honing tool and the work piece. The material removal is produced by the contact of the honing tool with the work piece. The present method and system is related to the significant simplification by using current digital control systems and various schemes to transfer rotational to linear mechanical systems (crank mechanism, four bar linkage). This control process is not limited to a ballscrew application as linear motion mechanism. It could be implemented in any system where the control feedback offered the dynamic output information. Examples of other applications for this process are machine tools where reciprocation is obtained by hydraulic cylinders controlled by a servo valve and position controlled by a linear encoder, and a servo motor link to a chain as motion transfer element.
The following lists are a simplified summary of other known honing systems' limitations and problems.
Known Honing Machine Stroking Technology:                1. Stroking output limited by moving mass.        2. Stroking system independent of feed or spindle system (very limited input/output relation to rest of machine).        3. Slow positioning feedback, position error.        4. Relative “geometry correction” depending on measuring last part to make system adjustments in next process part.        5. Slow pre and post process operations.        6. No operational changes depending on tooling or external variables.        7. Unique motion profile.        8. Limited stroke range.        9. Slow and complex dwell system.        10. Relative crosshatch angle.        11. No tool crash protection.        12. No safety control.        13. Complex mechanical system, two independent systems one to position and another one to stroke.        
A review of known patents illustrates how the use of electronic/feedback technology is wide spread throughout the machine tool industry. The specifics of the claims of these patents are related to the control and power transmission of this technology to improve or create new processes. The time line of these claims are not related to novel mechanical inventions but to the digital and control improvements produced in systems control and therefore in the machine tool industry. The use of already existent mechanical subsystems and its implementation produced improvements in the final output. Prior art is presented the following example U.S. patents:
C. Tuckfield.755,416circa 1904“Mechanism for converting reciprocating intorotary motion and vice versa”National Automatic Tool Company Inc.3,126,672circa 1964“Vertical Honing Machine”Barnes Drill Co.3,404,490circa 1968“Honing Machine with automatic force control”Siemens Aktiengesellschaft3,664,217circa 1972“Method and system for digital subdivision of thetool feed travel of a numerically controlledmachine tool”Sunnen Products Company4,035,959circa 1977“Cam operated automatic control for a honingmachine”Hitachi Ltd.4,143,310circa 1979“Apparatus for positioning”Rottler Boring Bar Co.4,189,871circa 1980“Honing machine”Hitachi Ltd.4,418,305circa 1983“Velocity Feedback Circuit”Alfred J. Raven III.4,423,567circa 1984“Power stroking honing machine and controlapparatus”Maschinenfabrik Gehring GmbH4,455,789circa 1984“Self-controlled honing machine”Textron Inc.4,534,093circa 1985“Beo-type Machining System”Maschinenfabrik Gehring GmbH4,679,357circa 1987“Method and apparatus for displacing a honingtool”Delapana Honing Equipment Limited4,816,731circa 1989“Honing Machine”Caterpillar Inc.5,426,352circa 1995“Automatic honing apparatus”HMR GmbH5,479,354circa 1995“Method for the computer-assisted control of amachine or process”
Each of the above mentioned patents are representative of improvements in the machine control system. Most illustrative of early systems is U.S. Pat. No. 755,416 C. Tuckfield “Mechanism for converting reciprocating into rotary motion and vice versa”, which shows the cycle motion repetition produced by the cam profile. Also, with the same importance are the U.S. Pat. Nos. 4,143,310 and 4,418,305, Hitachi's “Apparatus for positioning” and “Velocity Feedback Circuit”; where the main improvement is related to the feedback position and velocity, offering control and total dynamic system information. U.S. Pat. No. 4,816,731 “Honing Machine” by Delapena Honing Equipment Limited, clearly represented the use of digital control technology in a honing machine. The to same control is representative of the machining process in other equipment where the limitations were established by the control development not by the process. The mentioned patent clearly addresses all the actual honing technology problems except points 7 and 11 above. These two points are limited in their concept. The complete concept is itself limited by the technology utilized being in principle as slow as their control loop. U.S. Pat. Nos. 4,816,731, 4,621,455, 4,455,789, and 4,423,567 each represent a honing machine where there is a relative motion between the honing tool and the work piece. Also, the honing tool is expanding radially at the same time that it rotates. The removal of material is therefore produced by the honing tool surfaces being harder than the work piece.
In U.S. Pat. No. 4,816,731, column 7, lines 17 to 44, a unique motion profile is described. This motion profile is sectioned in 6 sub cycles: Forward acceleration, forward steady speed, forward deceleration, backward acceleration, backward steady speed, and backward deceleration. This acceleration profile per cycle produces uncertainties in the jerk output. These uncertainties are reflected in the position profile with inconsistency and vibrations throughout the mechanical components. This position error is clearly encountered by the honing machine of U.S. Pat. No. 4,816,731 (column 8, lines 1 to 14). The vibrations problem is also controlled by reducing possible output. This is described in column 6, lines 15 to 22. The problem is underlined on page 25, section 2.5 of “Cam Design and Manufacturing Handbook” by Robert L. Norton. It says “If we wish to minimize the theoretical peak value of the magnitude of the acceleration function for a given problem, the function that would best satisfy this constraint is the square wave . . . ” This function is also called constant acceleration. This function is not continuous. It has discontinuities at the beginning, middle and end of the interval. So by itself, is unacceptable as a cam acceleration function.”
A schematic representation of this motion profile is shown in FIG. 1 of the drawings. As represented in FIG. 1, the discontinuities of the acceleration function produce an infinite jerk output that violates the cam design corollary. In cycling motion, J1 and J6 are removed, given that the motion is linking from cycle to cycle. The other four discontinuities make the usage of this motion profile very limited.
The honing process is typically used to generate a straight bore or hole. This is a practical approach to the manufacturing process; the best practice would be a straight cylindrical shape under working conditions and with a uniform surface topology to ensure optimum lubricating conditions, usually achieved with a constant crosshatch through the to entire working bore. However, there are some applications, due to some physical change, for example thermal growth, assembly loads, bolts preload, etc., for which a different shape, that is, a non-cylindrical shape for at least a portion of the bore, would be better. Representative examples of special or non-cylindrical shapes include, but are not limited to, a taper running in a particular direction in all or part of the bore, or a barrel shape. For example, a honed bore having a barrel shape along at least a portion of the bore, as a result of being restrained in its functional operating environment may change to a cylindrical shape. And, there are also some applications wherein the working conditions of the work piece would be enhanced by a bore having a special shape, e.g., taper, barrel, etc. Other special shapes, including, but not limited to helical grooved shapes, rifling, and the like, are also desirable for some applications.
Currently in honing, some special or different shapes other than cylindrical can be generated by manually dwelling the honing tool and reducing the length of the honing stroke in the region of the special shape. A problem encountered with this approach is that it is not necessarily accurate in positioning and time so the finished part may not be within surface or geometry specifications.
Another manner of honing special shapes is by the oscillation of the honing tool, that is, reciprocatingly expanding and retracting of the honing element or elements, e.g., abrasive stone or stones during the stroking motion. For example, to generate a straight taper in the work piece, the honing tool is expanded as it is moved toward the larger end of the region of the bore, and then retracted as it is moved toward the smaller end. This expansion and contraction will typically be done during every stroke. However, a problem encountered with this approach is that the tooling required to expand and retract the stones accurately are very complex and is almost impossible to make in a small diameter. And, again, the ability to accurately control the position of the honing elements limits what surface and geometry specifications that can be met.
Thus, what is sought is a method and system which overcomes one or more of the problems and shortcomings set forth above.